Pulse signaling system



July 26, l1949. l P. K. CHATTERJEA ET AL 2,475,959

PULSE SIGNALLING SYSTEM Filed May '1, 1945 WML? Alto/111,51

Patented July 26, 1949 UNITED STATES OF Fil-CE PULSE 'SIGNALING SYSTEM Prafulla Kumar Chatterjea and Charles ThomasA Scully, London, England', assignors; by mesne assignments, to International- Standard: Elec` tric Corporation, New York,N.Y Y., a corporation of Delaware Application- May 1, 1945, Serial No. 591,270

Ih. Greaty Britain May 2,1 1944 7 Claims;

l. They present invention relates to electrical pulse signalling systems and has'forl itsobject to'pro'- videarrangements Vfor producing electrical pulsesl particularly timephase and duration-modulated pulses: Whoseunmod'ulated duration is very short, that is-very short compared to the repetition period of the-pulses, for example, of theorder of V"104725.

In accordance with the invention, an arrange*- mentl for producing modulated electrical pulses comprisesa normally inoperative or quiescent oscillation generator, which is-rendered operative olfactive byl a repetitive wave ofthe desired pulsefrequen'cy .once perV `period ofthe said' repetitive Wave; means-fonvaryingv a'factor of the arrangement Which'aiects a characteristic' of theigeneratedf Aoscillations by a modulation signal wave; forexample, varying the frequency of the repeti-V tive Wave to produce time-phasefmodul-ated pulses; or'thefrequency of the generatedA oscillations to producefduratiion'modulated pulses andl means for eliminatingtheposi-tivefor negative halfv cycles of the generated oscillations.

In order'to: produce duration modulated pulses, the frequencyv of the generated' oscillations is varied in accordance With'the amplitude of a' signal wave,- for example, by' varying the frequencydetermin-ingcircuitof the oscillation-gem erator. Thus-theperiod of the half-cycle of the generated'frequencyvaries in accordance withv the-lampliftude-of the modulating signal Wave and the instant of generatiionof the half cyclesis determined by the repetitive Waveof the desired pulse frequency; The'puls'esfin the output of the oscillation generator will'be substantially half sine -wavel-i-n formy and may be'transformed4 torectangular or other shape in a-n-y'lfnownmanner,y asl for example-,1v by4 amplifying and;k amplitude lim-iting-to'produce pulses of rectangular form;

To produce-time-phase modulated pulses, the source-of 'pulse-'repetition frequency is frequency or phase 'modulated' inaccordance with the amplitude-of' a'signal" wave. The frequency .of the oscillation generator is maintained Aconstant vbut the oscillations are generated at intervalsvv dependingrupon the frequency vof `thesource.` As in thev case of duration'modulation pulses', the pulses in theoutput of'the oscillation generator maybe shapedvin any. desired manner.

In an'ernbodimentfof vtheinvention about to be describedan electron4 discharge oscillation generator is .designed to produce oscillations `whose period-is twice the desired'mean duration .,offthe pulses `and to havethe negative.(Diapositive) h'al' Waves eliminated; isbi'assedto be normally in- 2: operative and is rendered operative -intermittently by a repetitive wave .of the desired pulse repetition frequencyV and the pulses in the output ofthe generator are modulated by modulating one of the factors governing one of the characteristics of 'the pulses, for example'the frequency, of therepetitivezwave which results in time-phase modulationv of" the generator output pulses, or the frequency vof vthe generator which results in durationmodulationNA of the pulses. In order to produce a single pulse "during each repetitive wave period; the repetitive Vwave is applied to the oscillation generator sothat' it renders'this latter operativefor'less than a period off the'oscillation generated.

The accompanying; drawings show by way of example, the' circuitv arrangements'V of two embodiments ofthe invention, in Figure 1 .for producing duration-modulated-pulses and in Figure '2 for producing time-phase modulated pulses.

in Figure 1 the arrangement comprises'anelectron discharge device oscillation, generator repre? sented as a triode Vl with a frequency determining circuit comprisingparallel connected induce tance'Ll and capacity'Cl connected in the anode circuit Vand coupled for regenerative feedback to the grid by inductive coupling'coil L2. In series in the grid-.cathode circuit is the auxiliary driving source 'Sofi the desired pulse repetition fre quency; This .sourcemay comprise a sinusoidal but'preferably'sawv tooth or other peak form of repetition. wave and the grid biasof the. valve VI is so;ad;usted that normally Vl is nonconductive but when the wave from auxiliary source S is applied, the valve becomesconductive and the oscillator becomes operativeat some point in the cycle of the wave. rlhe period of the oscillator is. adjusted vto be. twice the. desired duration o the required pulses and the amplitude of the waverom source -S' is adjusted, to be such that the oscillator is operative for notV more than a perodof the generated frequency and for not less than half' said period. A rectifier D is connectedacross the frequency determining` circuit Ll, C'I` of Vvalve Vl to absorb or eliminate alternate half cycles of the generated oscillation.

The bias on VI is. obtained by means of the resistancechain r2, .T31 connected across thehigh tension supply, and ,by varyingAV the relative values of r2 and r3; as will'be Well'understood. Resistancey His connected Vin the grid circuit, and the condenser` C2 is connected across r2 as is usual andV well known, The output pulses are taken fromjthe anode terminal shown atO.

To produce duration modulated pulses, accord;

drawing use is made of the Miller effect to vary the capacity of the frequency determining circuit and to this end a pentode valve V2 is connected across the valve oscillator circuit, that is, across the valve Vl and circuit LlC I in series and the modulating signal wave which may, for example, v

be speech, is applied to the control grid Gl of the pentode V2 to provide the capacity variation as is well known. Thus the period of the oscillations generated in the oscillator varieswith the signal wave amplitude and hence the pulses produced in the anode circuit, which consist of alternate half cycles of the oscillations are duration modulated'in accordance with the amplitude variation of the signal modulating wave. The half -oscillation pulses may be shaped into rectangular form by any known means, such as already stated, in the well known manner of amplifying and amplitude limiting.

Whilst a particular oscillation generator has been given byV way of example, it will be understood that any other type of oscillation generator may be utilised and any other means for varying the frequency under the control of the modulating signal wave may be employed. l

In order to obtain time phased modulated pulses, the arrangement shown in Figure 2 may be used. In this gure, parts the same as those in Figure 1 are given like designations.Y The valve V2 is omitted, and the frequency of the generated oscillations remains constant. However, any known means is provided for frequency or phase modulating the source VS Whose mean frequency is the desired pulse repetition frequency, by means of the modulating signal wave from source The source lS takes the form of a variable frequency oscillation generator, the waves being applied to control the operation of the oscillator. In the arrangement shown in Figure 2 means may be provided to maintain the frequency constant so that the duration of the output pulses `is maintained strictly constant.

As mentioned in relation to Figure 1, the pulses in the output of the arrangement shown in Figure 2 may be amplied and amplitude limited to produce pulses of rectangular wave form.

It will be easily seen by those versed in the art that to obtain amplitude modulated pulses from Vl' it is only necessary tomaintain the frequency of source S constant and to modulate the amplitude of these oscillations by the modulating signal wave before application to vary the bias on Vi or else to apply the modulating wave directly to the grid of Vl to vary the gain thereof.v

Referring again to Figure l, it may be found that the reactance valve V2 is required to present inductive or capacitive reactance in practice depending upon the type of oscillator circuit employed as well as the part of the circuit controlled by the reactance valve. l

The optimum design of coils Ll, L2 in the type of circuit shown in Figure 1 is the design which has the greatest coupling and Va moderate Q The tuning of such a circuit would thus avoid amplitude modification to any sensible extent.

In embodiments where the valve Vl, shown `in the example as a triode, is a multi-grid valve such as a pentode, the pulse repetition frequency from source S may be applied to other electrodes than 4 the control grid, for example to the suppressor grid and/or screen grid.

What is claimed is:

1. An arrangement for producing modulated electrical pulses comprising a normally inoperative oscillation generator, a source of repetitive waves, of the desired pulse frequency, means for applying waves from said source to said generator to render it operative once per period of the said repetitive wave, a source of signal waves, means for varying by modulating with the signal waves from said source a factor of the system which affects a characteristic of the generated oscillations, and means forY eliminating half-cycles of the generated oscillations of a given polarity.

2. An arrangement for producing modulated electrical pulses comprising an oscillation generator Vwhose period is twice the desired mean pulse duration, bias means for rendering said generator normally inoperative, an auxiliary generator of waves of pulse repetition frequency, means for applying the output of said auxiliary generator to render said oscillation generator operative once every repetitionperiod, means for eliminating alternate half cycles of the generated oscillations fromrsaid oscillation generator and means for varying the frequency of one of said generators in accordance Vwith the amplitude of a modulating signal.

3. An arrangement for', producing duration modulated electrical pulses comprising an oscillation generator of higher frequency than the pulse repetition frequency, bias means'for rendering said generator normally inoperative,` an auxiliary source of waves of pulse repetition frequency, means forapplying the output of said- Y auxiliary source to render theA said generator operative once. every said repetition period, means for eliminating half cycles of the generated oscillations of given polarity and means for varying the frequency of the generatedv oscillations in accordance with the amplitude of a modulating signal wave.

4. An arrangement for producing time-phase modulated electrical pulses comprising an oscillation generator of higherrfrequency than the mean pulse repetition frequency, bias means for rendering said generator Vnormally inoperative, an auxiliary source of waves of pulse repetition frequency, means for applying the output of said auxiliary source to render said generator operative once every said repetition period, means for eliminating half cycles of the generated oscillations of a given polarity and means modulatingV the angular velocity of the' waves of said auxiliary source in accordance with the amplitude of a modulating signal.

5. An arrangement as claimed in vpreceding claim 2 wherein ysaid oscillation generator comprises an electron discharge device whose grid is negatively biassed to render said generator normally inoperative, and means for applying the said repetitive wave form to said grid to overcome the negativeV biasy and render said generator operative.

6. An arrangement as claimed in preceding claim 2 wherein the said oscillation generator generates one oscillation per period of said repetitive wave. Y

7. An arrangement as claimed in ,claim 3 wherein the means for varying the frequency of the generated oscillations comprises an electron discharge device connected across thev frequency determining element of said generatorl and means for applying the modulating signal wave Vto saidr discharge device to vary the impedance thereof according to the amplitude of said signal wave. PRAFULLA KUMAR CHA'ITERJEA. CHARLES THOMAS SCULLY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 

